Crash cause by remove_observer

[noelwarren]

1. SketchUp/LayOut Version: SketchUp 2024
2. OS Platform: Windows

When you save a sketchup component, observers are incorrectly notified that new components have been added. Adding new observers to this definition and later removing them seems to cause crashes.

The below snippet expects to be used with the 2024 default template with the "Teddy" face me component

# class definitions
class DefinitionsObserver

    def initialize(model)
        @definition_observers = []
        model.definitions.add_observer(self)
        model.definitions.each { |definition| 
            observe_definition(definition)
        }
    end

    def onComponentAdded(definitions, definition)
        observe_definition(definition)
    end

    def observe_definition(definition)
        @definition_observers.push(DefinitionObserver.new(definition))
    end

    def disable
        @definition_observers.each(&:disable)
    end

end

class DefinitionObserver

    def initialize(definition)
        @definition = definition
        @definition.add_observer(self)
    end

    def disable
        @definition.remove_observer(self)
    end

end

# setup observers
active_model = Sketchup.active_model
definitions_observer = DefinitionsObserver.new(active_model)

# Setup a dummy definition
foo = active_model.definitions.add("foo") 
foo.entities.add_edges([0,0,0],[10,10,10])

# Add instance to "Teddy"
active_model.definitions["Teddy"].entities.add_instance(foo, Geom::Transformation.new)

# At this point right click on teddy, select "Save as" and save the component somewhere
# This triggers onComponentAdded for the "foo" component definition again, attaching a second observer

definitions_observer.disable # this will cause a crash when attempting to remove "foo"'s second observer 

[sketchup[bot]]

Logged as: SKEXT-4155